Northeast Fisheries Science Center Reference Document 01-14
Identification
of Seasonal Area Management Zones
for North Atlantic Right Whale Conservation
by Richard
L. Merrick, Phillip J. Clapham, Timothy V.N. Cole,
Patricia Gerrior, and Richard M. Pace, III
National Marine Fisheries Service, 166 Water Str., Woods Hole MA
02543
Print
publication date October 2001;
web version posted October 22, 2001
Citation: Merrick, R.L.; Clapham, P.J.; Cole, T.V.N.; Gerrior, P.; Pace, R.M., III. 2001. Identification of seasonal area
management zones for North Atlantic right whale conservation. Northeast Fish. Sci. Cent. Ref. Doc. 01-14;
18 p.
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EXECUTIVE
SUMMARY
Despite 30 years of protection under the Endangered Species Act,
the North Atlantic right whale (Eubalaena glacialis) has shown
little recovery. This lack of recovery is partially the result of
continued anthropogenic mortality, primarily due to ship strikes
and entanglement in fixed fishing gear. Between 1997 and 2000, NMFS
and the Atlantic Large Whale Take Reduction Team (ALWTRT) developed
and implemented an Atlantic Large Whale Take Reduction Plan to reduce
interactions with fishing gear. Some of the approaches in the Plan
deal with fishing gear modifications, while others involve fishing
time and area closures in right whale critical habitats. In February
2000, NMFS and the ALWTRT began to consider additional time and area
gear restrictions to further reduce anthropogenic interactions.
NMFS has proposed to implement these additional gear
restrictions using a two-pronged strategy. First, areas with predictable
annual concentrations of right whales will be considered for Seasonal
Area Management (SAM). Such areas would have specific boundaries and
pre-designated closing and opening dates. Specification of additional
SAM zones continues the management approach used in 1997 in establishing
the Cape Cod Bay and Great South Channel Restricted Areas for right
whale conservation (62 FR 39157). Second, areas without predictable
concentrations may be considered for Dynamic Area Management (DAM).
In these areas, restrictions would not be invoked unless concentrations
of right whales had been found by qualified observers. Once concentrations
were seen, NMFS could invoke a minimum two week restricted area around
the animals.
Herein, we present GIS analyses for defining SAMs based on the procedures
used by Clapham and Pace (2001) in defining DAMs. These analyses used
right whale sighting data collected on dedicated surveys conducted
by NMFS during March-July 1999-2001. In these surveys, 1,307 right
whales were observed in a total 784 different sightings.
The analytic process was to: (1) identify right whale sightings which
met the DAM trigger criteria during 1999-2001; (2) define and map a
core area around these sightings that also included a 15 nm radius
buffer for animal movements; ( 3) define SAMs for each of the three
years, by drawing polygons around the circular buffer zones, and joining
overlapping polygons ; (4) overlay all of the SAMs, identify and eliminate
SAM areas that were unique (i.e., only occurred in a single year, and
draw an outline around the aggregate SAM area; and (5) smooth the aggregate
SAM area to match existing closures and zone systems.
A Core SAM zone stretching from Cape Cod eastward to the Hague Line
was generated from the analyses. This zone could potentially be divided
into eastern and western zones based on observed seasonal differences
in right whale distribution during 1999-2001. A separate Northern SAM
zone was also elucidated but needs confirmation with additional future
survey effort.
INTRODUCTION
Despite 30 years of protection under the Endangered Species
Act, the North Atlantic right whale (Eubalaena glacialis) has
shown little recovery. Indeed, recent analyses suggest that survival
rates and population abundance levels have declined (Caswell et al.
1999). Lack of recovery is partially due to continued anthropogenic
mortality, due primarily to ship strikes and entanglement in fixed
fishing gear (National Marine Fisheries Service [NMFS] 1991). The 1994
amendments to the Marine Mammal Protection Act provided for the development
of take reduction plans to reduce interactions with commercial fishing
gear. On July 22, 1997, NMFS published an Atlantic Large Whale Take
Reduction Plan and also interim final regulations implementing this
Plan (62 FR 39157). The Plan contained a number of approaches to reducing
gear interactions. Some dealt with modifications to fishing gear, while
others dealt with fishing time and area closures in critical right
whale habitat areas. Since 1997, NMFS and the Atlantic Large Whale
Take Reduction Team (ALWTRT) have monitored right whale-fishing gear
interactions. Significant changes to the gear modifications included
in the Plan were made in February 1999 (64 FR 7529) and in December
2000 (65 FR 80368). In February 2000, NMFS and the ALWTRT began to
consider additional time and area gear restrictions to further reduce
interactions.
NMFS has proposed to implement these additional gear restrictions
using a two-pronged strategy. First, areas with predictable annual
concentrations of right whales will be considered for Seasonal Area
Management (SAM). Such areas would have specific boundaries and pre-designated
. Specification of additional SAM zones continues the management approach
used in 1997 in establishing the Cape Cod Bay and Great South Channel
Restricted Areas for right whale conservation (62 FR 39157). Second,
areas without predictable concentrations may be considered for Dynamic
Area Management (DAM). In these areas, restrictions would not be invoked
unless concentrations of right whales had been found by qualified observers.
Once concentrations were seen, NMFS could invoke a minimum two week
restricted area around the animals.
One of the first steps in developing area closures is to determine
a suitable threshold density of right whales which would trigger implementation
of such closures . Following considerable discussion by the ALWTRT
and completion of a research study by NMFS scientists (Clapham and
Pace 2001), the threshold density trigger was specified as a minimum
of 3 right whales within a 75nm2 area (ca. 0.04 right whales
per nm2). Also specified was the size of an area necessary
to contain a right whale's movements over a 1-2 week period. This was
a 15nm radius zone.
The Clapham and Pace (2001) study was used to design DAM zones. Here
we present additional analyses for defining SAMs. First, we provide
a brief summary of the 1999-2001 NMFS North Atlantic right whale survey
results. Secondly, we define geographic areas in the Gulf of Maine,
based on the trigger and buffer size analyses of Clapham and Pace (2001),
that could be considered as potential North Atlantic right whale Seasonal
Area Management zones.
METHODS
Surveys
Directed aerial surveys for North Atlantic right whales were conducted
by NMFS during March-July, 1999-2001 in the area from south of Nantucket,
MA northward to the Bay of Fundy, and from the New England coast eastward
to the Hague Convention Line (Figure 1). The
surveys were accomplished using two high-wing, twin-engine fixed wing
aircraft. One was a NOAA DeHaviland Twin Otter, and the other was a
chartered amphibious Grumman Widgeon (1999) or Goose (2000-2001). Surveys
were flown at ca. 230 m (1999-2000) or 310 m (2001) altitude, and 100
kts (185 km/hr). Flights were conducted by at least one aircraft on
virtually all days when sighting conditions were Beaufort 3 or better,
but were not performed when visibility was poor or obscured (snow,
rain or fog).
During 1999-2000, flights were either flown along tracklines developed
for SCOPEX (South Channel Ocean Productivity Experiment; Beardsley
et al. 1993; Kenney 1993) in the Great South Channel area, or were
directed towards areas of reported or suspected right whale concentrations.
In 2001, one aircraft flew a monthly series of east-west track lines
which overlaid the entire study area, while the second aircraft surveyed
the Great South Channel area and other offshore areas.
Survey protocols for the two aircraft were similar. Each typically
carried two observers and a recorder (in addition to two pilots). The
observers made continuous observations out of both sides of the aircraft,
with all sightings recorded on a laptop computer by the recorder. When
right whales, other marine mammals, marine turtles, sharks, or fish
schools were seen, the observer provided the recorder with the number
of animals observed by species, and other ancillary information . Because
the computer software had a direct GPS link, the location, date, and
time of all sightings were automatically recorded when observations
were entered. When right whales were seen, the aircraft typically broke
off the survey path to obtain 35 mm or digital photographs of the animals
for photo-identification.
Post-survey, the electronic survey data sets were audited /corrected
based on in-flight notes and edited for reasonableness. The data were
then reformatted for analysis.
Analysis
Analysis of the right whale sightings data involved the following
steps: :
1. Identify those right whale sightings which met the trigger criteria
(= events)
2. Define and map the core area
3. Define a 15 nm radius buffer around the core
4. For each year, draw polygon around the circular buffer zones, and join
overlapping polygons
5. Overlay the SAM areas from all three years, eliminate the SAM areas that
occurred only once during the three years, and draw an outline around the
remaining SAM areas
6. Smooth the remaining areas to account for existing closures and zone systems
Sightings from every survey day during 1999-2001 were reviewed to
identify events sufficient to trigger a Dynamic Area Management closure.
The trigger used was a sighting of three or more right whales sufficiently
close to one another to achieve a density of 0.04 right whales/nm2 (Clapham
and Pace 2001). This is equivalent to a minimum of 3 whales within
a 75 nm2 area. The latitude, longitude, number of animal
involved, and date and time of each event ) were recorded in a dBase
data set, and the events plotted using ARCView 3.1.
Whales sighted in an event were assumed to occupy a circular core
area with an average density of 0.04 right whales/nm2. This
core area was mapped by defining a circle around the centroid of the
event. The core area varied directly with the number of animals sighted.
That is, if 3 whales were sighted in an event the core area was ca.
75 nm2 (4.9 nm radius), with the area increasing to 100
nm2 (5.6 nm radius) for 4 animals, 125 nm2 (6.3 nm radius)
for 5 whales, etc.
A 15 nm radius buffer was then drawn around each core area to account
for animal movements (Clapham and Pace 2001). An event with 3 animals
and a core area of 75 nm2 (4.9 nm radius) would then have
a full circular protection zone of 1,244 nm2 (4.9 nm radius
+ 15nm radius = 19.9 nm radius; full protection circular zone area
= 
r2 =
1,244 nm2) .
SAM zones were mapped for each analysis year (1999-2001) by drawing
a simple polygon around each buffer area. Overlapping or adjoining
polygons were joined. This produced three annual sets of SAM zones.
What distinguishes DAM and SAM is the predictability of whale concentrations.
The Cape Cod Bay and Great South Channel Restricted Areas are examples
of SAM zones as they were based on sightings of right whales reoccurring
year after year in these areas. In our analyses, an area was considered
to be a candidate SAM area if right whales were observed in this area
during spring in all three years. If whales were observed in an area
in only one year or in different months in different years, then this
area was not considered as a candidate SAM area. We overlaid all three
years of SAM areas, eliminated areas which were applicable to only
one year, and drew boundaries around zones for the aggregate of years.
Finally, it was recognized that a number of groundfish and protected
species management areas already exist in the Gulf of Maine. NMFS and
the New England Fishery Management Council typically use a quarter
degree square grid to align these zones (for ease of interpretation).
The final boundaries of the SAM areas were therefore reconfigured somewhat
so as to align with these with existing management areas.
Areas of the SAMs were calculated in ARCView 3.1 using the U.S. referenced
Albers Equal Area Conical Projection.
RESULTS
Sightings
A total of 1,307 right whales were enumerated in 784 sightings during
the 1999-2001 NMFS aerial surveys (Table
1). This total does not include sightings by the Center for Coastal
Studies which surveyed the Cape Cod Bay Restricted Area. As a result,
the NMFS surveys contain very few sightings of right whales in Cape
Cod Bay, even though right whales commonly occur in the Bay during
late winter-early spring.
Few animals were seen outside of Cape Cod Bay in March (1.8%) or July
(5.6%; Table 2). Most animals were
seen in May (43.8%), June (32.3%) and April (16.4%), due in part to
greater sighting effort in these months.
Survey sightings in March-April (Figure 1, Figure 2, and Figure 3)
tended to be in the areas surrounding Cape Cod, MA (e.g., Provincetown
Slope). By May, however, right whales were regularly sighted along
the northern edge of Georges Bank and in the Great South Channel. Animals
were consistently seen in all three years in these areas and in the
Wilkinson Basin through June, with a tendency for animals to be seen
further north as the season progressed. During April and June in 1999
and 2000, right whale concentrations were observed in the Cashes Ledge
area. However, similar concentrations were not found in any month during
2001 (despite survey coverage of the Cashes Ledge area in three months).
Events
Concentrations of right whales meeting the triggering criteria occurred
149 times during 1999-2001. This included 38, 42, and 69 events in
1999-2001, respectively (Table 1).
The number of events peaked in May (67 events or 45% ), followed by
June (44 events or 30% ) and April (23 events or 15%) (Table
2). The fewest events occurred in July (9 events, 6%) and March
(6 events, 4% %).
The number of whales in events that met the trigger criteria ranged
from 3 to 29 (Figure 4). The average number
of whales in an event was 6.2 and average group size varied little
among years (5.7 to 6.7; Table 1).
Average group size was smallest in March (3.8), and ranged between
5.8 and 7.3 during r April through July (Table
2).
Seasonal Area Management Zones
A geographic zone drawn to encompass all 149 events (without buffers)
during March-July 1999-2001 enclosed a total area of about 10,200 nm2 (Figure 5). Enlarging the zone to include the buffer areas around the events
(Figure 6) increased the zone size to 17,000
nm2 (Figure 6).
Comparing SAM zones among the three years (Figure 7) revealed a consistent pattern in habitat use in areas outside
of the Great South Channel and Cape Cod Bay. Whales were consistently
seen in all three years in the area from Cape Cod eastward to the
Hague Line, but only sporadically occurred to the north (e.g., the
Cashes Ledge Area).
Aggregating the three annual SAM zones together (but excluding areas
where animals were seen only once in the three years), yielded the
aggregate SAM zone shown in Figure 8. Almost
all of 784 right whale sightings during the 1999-2001 NMFS aerial surveys
occurred within this aggregate zone.
Smoothing and realigning the aggregate SAM boundaries with existing
management areas produced two possible SAM zones (Figure 9). One is the Core zone (ca. 7,000 nm2) which extends
eastward from Cape Cod to the Hague Line and is where right whales
were consistently sighted in all three years. The other area is the
Northern zone (ca. 1,700 nm2 ), located to the north of
the Core zone, where right whale sightings occurred sporadically in
some months in two of the three survey years.
The Core zone, in combination with the existing Cape Cod Bay (CCB)
and Great South Channel (GSC) Restricted Areas, encompasses 134 (90%)
of the 149 events during 1999-2001. Of the 15 events not included,
4 were from 1999 (3 April, 1 May), and 11 from 2000 (all June). All
events from 2001 occurred in the combined Core/Restricted Area zone.
Of the 784 sightings, only 94 (12%) occurred outside of this zone,
with 64 of these sightings of single animals.
Within the Core zone, right whale events occurred more frequently
in the western part of the area (near Cape Cod Bay and the Great South
Channel) in March-April than in May-July (Figure 10). During March-April, 13 of the 15 events outside of the CCB
and GSC restricted areas occurred in the Core SAM zone west of 69.4
W longitude. Conversely, during May-July all of the events within the
Core SAM zone which were not in the GSC closure, were east of 69.4
W longitude. Hence, a possible break point is suggested in the seasonal
distribution of right whales in this area.
DISCUSSION
Apart from Cape Cod Bay and the Great South Channel, there are several
other areas in the Georges Bank/Gulf of Maine region where North Atlantic
right whales consistently aggregate each spring. Despite less complete
survey coverage in the Core SAM zone than in the GSC area (Figure 8), the number of right whale events (49) in the SAM zone during
1999-2001 was comparable to that in the GSC (66). As such, implementation
of the Core SAM zone would afford significant additional protection
to right whales from interactions with fishing gear and ship strikes.
The protection afforded to right whales by the Northern SAM zone is
less clear, as it is presently uncertain as to whether the events in
this zone are reflective of predictable distribution patterns. The
1999-2001 NMFS aerial surveys in this area only detected right whale
concentrations in April-May 1999 and in June 2000. No such concentrations
occurred in 2001, despite increased survey effort. Aerial survey work
in 2002 and 2003 should help clarify right whale distribution patterns
in the Northern Zone area.
During 1999-2001, NMFS survey coverage was adequate in the Core SAM
zone and in the GSC area and was supplemented by excellent survey coverage
in the CCB area by the Center for Coastal Studies. Outside of these
areas/zones, annual coverage during 1999-2001 included only occasional
surveys of reported right whale "hot spots" (e.g., the Cashes
Ledge area). Thus, the lack of observations of right whales outside
of the well-covered survey areas may be as much a function of survey
effort as it is the absence or presence of right whales. It is hoped
that the surveys planned for 2002-2003 will resolve this issue.
Since all of the aerial survey effort to date has been limited to
late March-early July period, the distribution of right whales in other
months has not been captured. While it is well known that some right
whales are present in Cape Cod Bay and the Georgia-Florida critical
habitat area during December-March, most right whales are elsewhere
at the winter period. Even in mid-summer and early fall when many right
whales are concentrated in the Bay of Fundy, large number of whales
occur elsewhere. New survey efforts need to be conducted in the Gulf
of Maine during the fall-winter period to determine whether right whales
are using this habitat during this time of year.
The lack of synoptic spatial and temporal coverage becomes obvious
when sighting observations are corrected for sighting effort. Such
an analysis (R. Pace, unpubl. data) yields a checkerboard of blank
cells interspersed with a few cells with observations. One point seems
clear, however, high whale densities occur in the GSC in part because
of the large sighting effort in this area. Ongoing work at the NEFSC
and the New England Aquarium to correct sightings for effort, coupled
with additional surveys, should provide improved estimates of right
whale habitat use.
Despite several shortcomings with the existing survey data, it is
evident that that there are areas (i.e., the Core zone) where right
whale persistently aggregate which are outside of the areas officially
designated as critical habitat. Such areas should be considered for
inclusion as critical right whale habitat and as prime candidates for
Seasonal Area Management.
ACKNOWLEDGMENTS
We gratefully acknowledge the efforts of the survey teams and pilots
(NOAA and private). Without their efforts over the past three years
this report would not have been possible to produce. Surveys were authorized
under MMPA/ESA permit 917. We are grateful for the thorough review
of an earlier version of this manuscript by Dr. Fred Serchuk.
LITERATURE
CITED
Beardsley, R., R. Limeburner, P. Cornillon, A. Durbin, E. Durbin,
R. Kenney, H. Winn, K. Wishner, and M. Macaulay. 1993. SCOPEX, a Multidisciplinary
Study of Right Whale - Ecosystem Interactions. U.S. GLOBEC NEWS Number
3.
Caswell, H., M. Fujiwara, and S. Brault. 1999. Declining survival
probability threatens the North Atlantic right whale. Proceedings of
the National Academy of Sciences, USA. 96:3308-3313.
Clapham, P. J., and R. M. Pace, III. 2001. Defining Triggers for Temporary
Area Closures to Protect Right Whales from Entanglements: Issues and
Options. Northeast Fish. Sci. Cent. Ref. Doc. 01-06; 28 p. Available
from: National Marine Fisheries Service, 166 Water Street, Woods Hole,
MA 02543-1026.
Kenney, R.D. 1993. SCOPEX: A multi-disciplinary oceanographic study
of Right Whale feeding habitat in the Gulf of Maine. Abstract Tenth
Biennial Conf. Biol. Mar. Mamm.:1.
National Marine Fisheries Service. 1991. Final Recovery Plan for the
Northern Right Whale (Eubalaena glacialis). Prepared by the Northern
Right Whale Recovery Team for the National Marine Fisheries Service,
Silver Spring, MD. 86 p.
